Internal combustion engines are typically provided with starter systems for initiating operation of the engine. Starter systems often include an air motor driven by pressurized air and a gear system. Pressurized air is introduced to the air motor, causing a rotor to rotate. The rotor, which has a higher number of revolutions per minute (rpm) than what is needed to start the engine, is connected to the gear system, which includes one or more speed reducing gears configured to match the air motor rpm to the engine rpm. The reducing gears drive an output device such as a pinion, which is coupled to the engine. Rotation of the pinion in turn rotates the engine, initiating operation of the engine.
The force of the pressurized air or other fuel used to operate the starter system on the rotor can generate an axial load on the rotor that can more rapidly fatigue the rotor and other parts of the starter system. The bearing on which the rotor rotates may be able to withstand the axial load without excessive wear on the bearing or other parts. In other starter system configurations, where the axial load is considerable, specialized bearing configuration may be provided to overcome or compensate for the axial load. For example, larger bearings, double or stacked bearings, or angular contact bearings may be used. However, larger bearings and double or stacked bearings are not always useful due to space restrictions, and angular contact bearings are not always feasible due to cost constraints.